The invention relates in general to gas generating initiators and in particular to gas generating initiators including a filter that prevents large particles from entering the generated gas stream.
FIG. 1 is a sectional view of a prior art gas generating initiator 10. Initiator 10 may be used in applications such as the launching of sonobuoys from aircraft, ejector seats in aircraft and the initiation of ballistic munitions.
Initiator 10 includes a generally cylindrical body 12 that defines an initiator chamber 14. The body 12 is open at one end 11 and closed at a second end by a base 13. The body 12 has a central longitudinal axis Axe2x80x94A. The base 13 includes a generally centrally located passage 15. Passage 15 has one end on an interior surface 17 of the base and a second end on an exterior surface 19 of the base. A longitudinal axis of the first passage 15 is substantially coincident with the axis Axe2x80x94A of the body 12. Adhesive is applied to the threads of a filter 30, discussed in more detail below, which is then threaded into passage 15. Body 12 and filter 30 may be made of, for example, aluminum, aluminum alloy, steel or steel alloy.
Initiator 10 includes a charge holder 16 disposed in the open end 11 of the body 12. The charge holder 16 includes a consumable membrane 18 at one end and gas generating propellant 20 disposed in the charge holder 16. Charge holder 16 may be made of plastic and snap fit into chamber 14. Consumable membrane 18 may be made of nitrocellulose. A cap 22 is attached to the open end 11 of the body 12, by, for example, threaded engagement. An igniter 24 is disposed in an opening in the cap 22 and extends into the charge holder 16. The igniter 24 ignites the propellant 20 in the charge holder 16. A firing mechanism 26 is connected to the igniter 24 for firing the igniter. The firing mechanism may be activated, for example, manually or by a variety of switches, such as inertial switches, accelerometers, etc.
In ballistic applications, gas exiting the passage 15 is routed to a munition by using a nipple 28 attached (for example, with threads) to the base end 13 of the initiator body 12. The nipple 28 includes a passageway 29 therethrough to provide a conduit for gas generated by the initiator.
FIGS. 2a-2c show details of a prior art filter 30. FIG. 2a is a top view of the filter 30 showing a hexagonal head 32. FIG. 2b is a sectional view along the line bxe2x80x94b of FIG. 2a. FIG. 2c is a sectional view along the line cxe2x80x94c of FIG. 2b. Head 32 is joined to a shank 34. The shank 34 is threaded and threads into passage 15. Head 32 includes five radial gas passages 36 that intersect in the center of head 32. The five radial passages 32 join an axial passage 38.
In use, the initiator 10 is operated by firing the firing mechanism 26 which sends an electric signal to igniter 24. Igniter 24 ignites propellant 20 thereby generating gas. Consumable membrane 18 bursts and/or burns and the generated gas enters the filter 30 via the five radial passages 32, then enters the axial passage 38 and then exits the initiator via passage 15. The radial passages 32 in filter 30 are small enough to prevent any large particles of propellant or pieces of charge holder 16 from entering passage 15.
Because of the relatively small size of initiator chamber 14 (diameter may be as small as 0.035 inches), it is difficult to machine the even smaller filter 30. In addition, adhesive must be applied to the threads on filter 30 and then the filter must be threaded into the passage 15. The present invention eliminates the separate filter 30, thereby saving the time and money of fabricating filter 30 and assembling filter 30 into initiator 10.
It is an object of the invention to provide a gas generating initiator having a drilled-in integral multi-port filter.
It is another object of the invention to provide a gas generating initiator with fewer parts than the prior art to thereby simplify manufacture and assembly.